The present invention relates to an axle for heavy vehicle applications, and more particularly to forming an integral bearing shoulder in a tubular axle.
As a part of the production of axles, a shoulder is required as a back-up for the bearings which are assembled to the axle. The bearing shoulder is a stepped-up section of the spindle and is typically formed intermediate the spindle and axle diameter. The bearing fits onto the spindle at each end of the axle and the shoulder supports the bearing.
There are several known methods to produce this shoulder. One method is to manufacture an axle from a solid bar of steel. The entire axle, spindle and shoulder are directly produced from the steel bar. Other methods manufacture the axle as a tube with spindles welded to each end. These spindles also have a shoulder forged into them to provide the bearing support.
Yet another method is to form the spindle onto the end of the tubing and weld a collar onto the formed spindle to produce the bearing shoulder. This has proven to be an effective method for the production of semi-trailer axles. However, a machined component and a welding operation are required. Although practical, this does increase the finished axle cost.
Attempts to form the shoulder directly from axle tubing have required the use of temperatures in excess of 2000 degrees Fahrenheit in a localized area. This temperature is above the transition temperature of steel which has previously not allowed the use of heat treated tubing. The non-heat treated tube must be subjected to a quench and temper operation after forming to provide a tube having the desired strength for an axle. This increases the manufacturing complexity and also increases the finished axle cost.
Accordingly, it is desirable to provide an economical method for forming a tubular axle having the bearing shoulder directly formed into the tubing.